Memory devices are integrated circuits in which information may be stored and from which information may be extracted when desired. Each memory device is built from a plurality of memory cells. Each memory cell memorizes a bit of data. Although a bit of data seems insignificant, it may determine whether the stored information is correct, such as an amount in a bank account.
A memory cell may become defective because of imperfect manufacturing practices or degradation over time. Such defects render the memory device inoperative or unreliable. Instead of ridding memory devices with defective memory cells, the semiconductor industry turns to various techniques to salvage these memory devices.
One technique employs redundancy circuits. Redundancy circuits include a number of nondefective memory cells that can replace defective memory cells in memory devices. Redundancy circuits do not physically replace the defective memory cells but logically replace them. Redundancy circuits detect whether defective memory cells exist, configure memory devices to avoid the defective memory cells, and redirect memory accesses from the defective memory cells to the nondefective memory cells.
The act of configuring uses fuse circuits, which include fuses that can be blown to support the act of configuring. Previous generations of fuse circuits are incompatible with the memory devices of today, which use voltage supplies as low as 1.65 volts. Certain previous generations of fuse circuits also tightly integrate fuses and latches. Such integration causes inflexibility that is undesirable.
Thus, what is needed are devices and methods to enhance fuse circuit configurations in low-voltage integrated circuits, such as flash memory devices.